You are looking at preliminary documentation for a future release. Not what you want? See the current release documentation.
Logstash outputs remove
@metadata fields automatically. Therefore, if Logstash instances are chained directly or via some message
queue (for example, Redis or Kafka), the
@metadata field will not be available in the final Logstash instance.
@metadata fields, use the Logstash mutate filter with the rename setting to rename the fields to
Intro to Kibana
ELK for Logs & Metrics